The present invention relates to improvements in current-to-pressure (I/P) transducers of uncomplicated form which can operate swiftly and precisely although rendered highly immune to mechanical disturbances such as those of vibration, and, in one particular aspect, to unique high-performance I/P equipment of rugged and simplified construction having a movable bleed-valving armature advantageously fashioned as an electrically-unexcited lightweight thin blade pivoted transversely by an adjustable-torque taut band, magnetic material of the blade being disposed in a gap-shunting interacting relation with the core of a stationary electromagnet, and either of two flapper-valve portions of the same blade being in valving relation to a nozzle whose controlled leakage regulates an output pressure.
Control of pneumatic output pressures in accordance with electrical signals applied to bleed-type electromagnetic valving is a well-established practice, typically with the objective of supplying appropriate operating pressures to a pneumatically-actuated fluid-flow valve disposed in a system flow path. For such purposes, the needed operating pressures are commonly derived from a main pressurized source with the aid of a flow restriction and a leakage port, the latter being variably throttled by a movable valving member whose positions are automatically regulated electromagnetically. In the latter connection, so-called current-to-pressure (I/P) transducers provide the throttling function, in response to system control signals which, making good use of natural characterisitics and capabilities of modern electronic equipment, are preferably in the form of electrical currents. Such control signals have been driven through movable coils interacting with stationary permanent magnets, for example, thereby developing forces needed to adjust throttling by a levered valving member; U.S. Pat. Nos. 2,964,051 and 4,336,819 describe apparatus of that type. In other arrangements the coils have been held stationary, as parts of electromagnets which interact with and effect movements of magnetic material, and, which, in turn, cause related throttling movements of a valving member. Examples of such stationary-coil transducers are disclosed in U.S. Pat. Nos. 3,155,104, in which a hinged lever carries an armature attracted to the electromagnet, and U.S. Pat. No. 3,768,772, in which the movements of an armature and its associated valve member are kept linear by a parallelogram-type spring support, and U.S. Pat. No. 3,982,554, in which a flapper valve member pivots over a nozzle in the magnetic path of an electromagnet, and U.S. Pat. No. 4,579,137, in which a plastic diaphragm mounts a magnetic button over a nozzle formed in the center post and core of a special form of electromagnet. For I/P transducers to operate at the rapid speeds and with the precise repeatabilities needed to insure high-quality performance, their mechanically-movable components should not involve either large mass or superfluous or uncertain restraints. The moving-coil versions, which require flexible electrical connections, tend to offend in both respects and the problems with stationary-coil versions tend more to be concerned with armature inertia and with associated supports which allow for needed throttling motions. As is explained in detailed disclosures which follow, unique and improved transducers of a stationary-coil type advantageously employ a special taut-band armature suspension and restraint; prior moving-coil measuring instruments have utilized other forms of taut band, U.S. Pat. No. 3,277,370 providing an example of same.